Acessibilidade / Reportar erro

The synthesis of new isochromanylacetylarylhydrazones designed as probable non-addictive analgesic agents

Abstracts

The synthesis and pharmacological profile as analgesic and anti-inflammatory agents of new isochromanylacetylarylhydrazone derivatives (3) are described in this paper. The synthetic route used in this work to construct the heterocyclic six member ring explored a Lewis acid-catalyzed cyclization process as the key step, which represents a modified Friedel-Crafts reaction. These new derivatives (3) were obtained in ca. 85 % overall yields from the starting material safrole (4), an abundant natural product isolated from Sassafras oil. The NMR spectral analysis of these new derivatives indicated, at the C=N double bond level, the diastereomeric nature in a 70:30 ratio, where the major compound is the (E)-isomer. The results obtained from the pharmacological evaluation of (3) using the carrageenan-induced rat paw edema test and the acetic acid solution-induced constrictions in mouse test, indicated the pharmacophoric nature of the acylarylhydrazone moiety to the analgesic activity observed in this series.The role of the aryl substituents in the bioactivity seems to indicate that the presence of hydrophobic groups may improve the analgesic profile. These new isochromanylacetylarylhydrazone derivatives (3) represent a new class of non-addictive analgesic agents.

analgesic agents; isochromanylacetylarylhydrazones


A síntese e o perfil anti-inflamatório e analgésico dos novos agentes isocromanilacetilarilidrazônicos são descritos neste artigo. A rota sintética utilizada neste trabalho explora como passo chave para a construção de um anel heterocíclico de seis membros, a ciclização catalisada por um ácido de Lewis, que representa uma modificação da reação de Friedel-Crafts. Estes novos derivados (3) são obtidos em ca. de 85% de rendimento, a partir do safrol (4) utilizado como produto natural abundante, isolado do óleo de Sassafrás. A análise dos espectros de RMN destes novos derivados indica a natureza diastereoisomérica a nível da ligação C=N, na razão de 70:30, onde a maior contribuição é relativa ao isômero (E). Os resultados obtidos da avaliação farmacológica de (3) no teste do edema de pata de rato induzido por carragenina e no teste de contorções abdominais induzidas pelo ácido acético, indicam a natureza farmacofórica da unidade acilidrazona para a atividade analgésica observada nesta série. O papel dos substituintes na sub-unidade arila na atividade farmacológica parece indicar que a presença de grupos hidrofóbicos podem elevar o perfil analgésico. Estes novos derivados isocromanilacetilarilidrazônicos (3) representam nova classe de agentes analgésicos não-convencionais.


Article

The Synthesis of New Isochromanylacetylarylhydrazones Designed as Probable Non-Addictive Analgesic Agents

Margareth Rôse L. Santosª, Eliezer J. Barreirob * , Raimundo Braz-Filhoc, and Ana Luisa P. Mirandab

aCurso de Pós-Graduação de Química Orgânica, Universidade Federal Rural do Rio de Janeiro,23851-970 Seropédica, Rio de Janeiro - RJ, Brazil

bLaboratório de Avaliação e Síntese de Substâncias Bioativas (LASSBio), Faculdade de Farmácia, Universidade Federal do Rio de Janeiro, 21910-240 Rio de Janeiro - RJ, Brazil, e-mail:eliezerb@unikey.com.br

c Setor de Química de Produtos Naturais, LT-CCTA, Universidade Estadual do Norte Fluminense, 28015-620 Campos, Rio de Janeiro - RJ, Brazil

Recieved: March 29, 1996; December 2, 1996

A síntese e o perfil anti-inflamatório e analgésico dos novos agentes isocromanilacetilarilidrazônicos são descritos neste artigo. A rota sintética utilizada neste trabalho explora como passo chave para a construção de um anel heterocíclico de seis membros, a ciclização catalisada por um ácido de Lewis, que representa uma modificação da reação de Friedel-Crafts. Estes novos derivados (3) são obtidos em ca. de 85% de rendimento, a partir do safrol (4) utilizado como produto natural abundante, isolado do óleo de Sassafrás. A análise dos espectros de RMN destes novos derivados indica a natureza diastereoisomérica a nível da ligação C=N, na razão de 70:30, onde a maior contribuição é relativa ao isômero (E). Os resultados obtidos da avaliação farmacológica de (3) no teste do edema de pata de rato induzido por carragenina e no teste de contorções abdominais induzidas pelo ácido acético, indicam a natureza farmacofórica da unidade acilidrazona para a atividade analgésica observada nesta série. O papel dos substituintes na sub-unidade arila na atividade farmacológica parece indicar que a presença de grupos hidrofóbicos podem elevar o perfil analgésico. Estes novos derivados isocromanilacetilarilidrazônicos (3) representam nova classe de agentes analgésicos não-convencionais.

The synthesis and pharmacological profile as analgesic and anti-inflammatory agents of new isochromanylacetylarylhydrazone derivatives (3) are described in this paper. The synthetic route used in this work to construct the heterocyclic six member ring explored a Lewis acid-catalyzed cyclization process as the key step, which represents a modified Friedel-Crafts reaction. These new derivatives (3) were obtained in ca. 85 % overall yields from the starting material safrole (4), an abundant natural product isolated from Sassafras oil. The NMR spectral analysis of these new derivatives indicated, at the C=N double bond level, the diastereomeric nature in a 70:30 ratio, where the major compound is the (E)-isomer. The results obtained from the pharmacological evaluation of (3) using the carrageenan-induced rat paw edema test and the acetic acid solution-induced constrictions in mouse test, indicated the pharmacophoric nature of the acylarylhydrazone moiety to the analgesic activity observed in this series.The role of the aryl substituents in the bioactivity seems to indicate that the presence of hydrophobic groups may improve the analgesic profile. These new isochromanylacetylarylhydrazone derivatives (3) represent a new class of non-addictive analgesic agents.

Keywords: analgesic agents, isochromanylacetylarylhydrazones

Introduction

Several cell mediators have been proposed to play a role in inflammatory processes and hyperalgesia, since these compounds caused a decrease in pain thresholds1. The prostaglandins PGs, in particular, have been suggested to play a major role in the pathogenesis of inflammation and in the production of inflammatory pain2-4. The recent disclosure of two distinct forms of cyclooxygenase (COX, prostaglandin-H synthase or PGHS)5 indicated new directions for therapeutic approaches to inflammatory diseases6, confirming the role of icosanoids, produced by the COX enzyme which catalyzes the first two steps in the biosynthesis of PGs, producing the prostaglandin endoperoxide G2 and H2, precursors of all PGs. COX is the site of action of non-steroidal anti-inflammatory agents (NSAIS), and it is accepted that this is the basis of the anti-inflammatory action of these drugs7. The role of a second enzymatic pathway, namely 5-lipooxygenase (5-LO) in inflammation is also well known8. From arachidonic acid (AA), this enzyme produces the leucotrienes (LTs) which present chemotactil and bronco-constriction properties, also playing an important role in some chronic inflammatory diseases9.

In an effort to develop new synthetic bioactive compounds, as part of a research program aiming at the synthesis and pharmacological evaluation of new non-addictive analgesic and anti-inflammatory agents10-17, we have previously described the synthesis and the anti-edematogenic properties of the isochromanyl acid derivatives (1)16. These compounds showed significant anti-inflammatory and analgesic activity, reducing the edema in the carrageenan induced the rat paw testwith a dose of 25 mg/kg, and in reducing the number of constrictions in the acetic acid solution-induced test in mice with the same dose p.o. A second series of compounds, belonging to the acylhydrazone pyrazolic derivatives (2)18 was also synthesized and pharmacologically evaluated for analgesic properties. These derivatives presented powerful activity in the mouse abdominal constrictions test induced by acetic acid11. The most potent compound of this series (2a, W=N(CH3)2) exhibited eleven times the analgesic activity of dipyrone in the same test at equimolar doses (ED50 = 15.8 mg/kg; P = 0.05). These results led us to identify compound (3) as an attractive new target in the search for new anti-inflammatory and analgesic compounds. This new class of derivatives was designed as a structural hybrid of both (1) and (2), previously synthesized and elected as `lead compounds, as shown in Scheme 1.

In this paper we describe the synthesis and pharmacological profile of these new isochromanylacetylaryl hydrazone derivatives (3), using safrole (4), an abundant natural Brazilian product available from Sassafras oil (Ocotea pretiosa Mer., Lauraceae), as the synthetic starting material19.

Experimental

Chemistry

Melting points were determined with a hot-plate apparatus and were not corrected. Infrared (IR) spectra were obtained with a Perkin-Elmer 1600-FT spectrometer using potassium bromide pellets. Nuclear magnetic resonance (1H-NMR and 13C-NMR) spectra were recorded in deuterochloroform containing ca. 1% TMS as an internal standard with a Bruker AC-200 FT at 200 MHz (1H) and 50.3 MHz (13C). Chemical shifts are expressed in ppm (d) relative to TMS (= 0 ppm). Splitting patterns are as follows: s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet; br, broad. The mass spectra were obtained with a GC/VG Micromass 12 at 70 eV. The progress of all reactions was monitored by thin layer chromatography (TLC), using precoated Merck silica gel 60 F254 aluminum plates; detection was done with UV and I2. For column chromatography, Merck silica gel (70-230 mesh) was used. Solvents used in the reactions were generally redistilled prior to use and stored over 3A molecular sieves.

Ethyl ester of 1-(1-methyl-6,7-methylenedioxy)-isochromanyl- acetic acid (5)16

Ethyl acetoacetate (1.80 g;10.98 mmol) was added to a solution of homopiperonilic alcohol (8) (1.62 g, 12.6 mmol) in dry benzene (30 mL). A catalytic amount of p-toluenesulfonic acid (ca. 0.2 g) was added to the flask equipped with a Dean-Stark trap, and the reaction mixture was refluxed for 12 h. The solvent was removed under reduced pressure, affording a pale yellow oil which was dissolved in ethyl ether (ca. 30 mL). The oil was washed with a 30% aqueous sodium hydroxide solution. The organic layer (negative FeCl3 test) was dried over sodium sulfate, filtered, evaporated, and then chromatographed on a silica gel column (n-hexane:ethyl acetate, 9:1) to give the desired product (5) in a 75% yield. Its IR and 60 MHz 1H NMR have already been described16. New data are reported.

M.S. (70 eV): 278 (7%); 191 (100%); 149 (9%); 110 (31%).

1H-NMR (200 MHz) CDCl3/TMS d: 6.56 (s,2H, H-5 and H-8); 5.9 (s,2H, OCH2O); 4.10 (q,2H,OCH2CH3); 3.91 (m,2H, H-3); 2.90 (d,J = 13.5;1H, H-11); 2.73 (d,J = 13.5;1H, H-11); 2.71 (m,2H,H-4); 1.27 (s,3H, H-13); 1.20 (t,3H,OCH2CH3).

13C-NMR (50.3 MHz) CDCl3/TMS d:169.98 (C=O); 145.94 (C-6); 133.78 (C-7); 125.45 (C-9); 115.88 (C-10); 108.28 (C-5); 105.18 (C-8); 100.63 (OCH2O); 75.20 (C-1); 60.11 (OCH2CH3); 60.01 (C-3) 46.40 (C-11); 29.60 (C-4); 27.00 (C-13); 12.00 (OCH2CH3).

1-(1-Methyl-6,7-methyleneioxy)-isochromanyl-acetylhydrazide (6).

An ethanolic solution of ester (5) (1.30 g; 4.65 mmol) in 25 mL of ethanol was heated under stirring until complete dissolution. Then 4.7 mL of 85% hydrazine hydrate was added, and the reaction mixture was stirred at reflux for 3 h. At the end of the reaction (as indicated by TLC analysis) the product (6) was isolated by concentration of the reaction mixture under reduced pressure. Cold water was added and the resulting product (6) was filtered to give 1.10 g (85%) of a white solid.

m.p.:154-155 °C.

I.R. (KBr) n: 3360 (NH) ; 1670 (C=O) cm-1.

M.S. (70 eV) m/z,: 264 (13%); 192 (24%); 191 (100%) 115 (7%) 91 (6%); 77 ( 5%).

1H-NMR (200 MHz) CDCl3/TMS d: 7.76 (br. s,1H,NH); 6.53 (s,1H, H-8); 6.50 (s,1H,H-5); 5.87 (m,2H,OCH2O); 3.85 (m,2H,H-3); 3.76 (br. s,2H,NH2); 2.60 (m,2H,H-4); 2.73 (m,1H,H-11); 2.68 (m ,1H, H-11); 1.48 (s,3H,H-13).

13C-NMR (50.3 MHz) CDCl3/TMS d: 170.70 (C=O); 146.16 (C-6,7); 132.61 (C-9); 125.97 (C-10); 108.21 (C-5); 105.26 (C-8); 100.73 (OCH2O); 75.42 (C-1); 59.47 (C-3); 47.38 (C-11); 29.00 (C-4); 27.09 (C-13).

The general procedure for preparing 1-(1-Methyl-6,7-methylenedioxy)-isochromanyl-acetylarylhydrazones (3a-3g)

Benzaldehyde or its derivative (0.57 mmol) was added to a solution of hydrazine derivative (6) (0.15g; 0.57 mmol) in absolute ethanol, in the presence of two drops of hydrochloric acid as a catalyst. The end of the reaction was detected by TLC and the new hydrazones (3a-3g) were isolated by the concentration of the reaction mixture under reduced pressure and the addition of cold water to furnish the desired product as a colored precipitate in an 80% yield (Table 1). The E and Z isomers could not be separated, but their 1H and 13C assignments could be made from their higher field 2D spectra (1Hx1H-COSY, 1Hx13C-COSY,COLOC).

1-(1-Methyl-6,7-methylenedioxy)-isochromanyl-acetylarylhydrazone of benzaldeyde (3a-(E),(Z))

m.p.: 78-80 °C

I.R:. (KBr) n: 3430, 3200 (NH); 1664 (C=O) cm-1.

M.S. (70 eV) m/z: 352 (3%); 208 (8%); 192 (14%); 191 (100%); 170 (11%).

(E) Isomer

1H-NMR (200 MHz) CDCl3/TMS (d = ppm): 9.83 (s,1H,NH); 8.00 (s,1H,H-7); 7.70 (m,2H,H-26); 7.4 (m,3H,H-35,4); 6.59 (s,1H,H-8); 6.50 (s,1H,H-5); 5.9 (s,2H,OCH2O); 4.1 (m,2H-3);2.9 (m,2H-11); 2.8 (m,2H-4);1,56 (s,3H-13).

13C-NMR (50.3 MHz) CDCl3/TMS (d = ppm): 166.45 (C=O); 147.10 (C-7); 146.37 (C-7); 146.25 (C-6); 133.48 (C-1); 132.34 (C-9); 130.12 (C-4); 128.39 (C-35); 127.46 (C-26); 126.48 (C-10); 100.80 (OCH2O);75.97 (C-1);59.72 (C-3);48.37 (C-11) ;29.18 (C-4);27.20 (C-13).

(Z) Isomer

1H-NMR (200 MHz) CDCl3/TMS (d = ppm): 9.18 (s,1H,NH); 7.70 (s,1H,H-7); 7.61 (m,2H,H-26); 7.4 (m,3H,H-35,4); 6.66 (s,1H,H-8); 6.52 (s,1H,H-5); 5.9 (s,2H,OCH2O); 4.0 (m,2H-3); 3.46 (d,J = 14, 1H-11); 3.10 (d,J = 14, 1H-11); 2.75 (m,2H-4);1.63 (s,3H-13).

13C-NMR (50.3 MHz) CDCl3/TMS (d = ppm): 172.87 (C=O); 143.75 (C-7); 145.89 (C-7); 145.77 (C-6); 134.58 (C-9); 133.85 (C-1); 129.76 (C-4); 128.54 (C-35); 126.91 (C-26); 125.79 (C-10); 100.60 (OCH2O); 75.88 (C-1); 59.86 (C-3); 42.49 (C-11); 29.24 (C-4); 28.36 (C-13).

1-(1-Methyl-6,7-methylenedioxy)-isochromanyl-acetylarylhydrazone of 2-furaldeyde (3b-(E),(Z))

m.p.: 88-91 °C

I.R.(KBr) n: 3450, 3215 (NH); 1670 (C=O) cm-1.

(E) Isomer

1H-NMR (200 MHz) CDCl3/TMS (d = ppm): 9.79 (s,1H,NH); 8.21 (s,1H,H-5); 7.46 (s,2H,H-4); 7.24 (s,2H,H-26); 6.67 (m,2H,H-35); 6.57 (s,1H,H-8); 6.49 (s,1H,H-5);5.88 (s,2H,OCH2O); 3.8 (m,2H-3); 2.65 (m,2H-4); 2.87 (d,J = 14, 2H-11); 2.83 (d,J = 14, 2H-11); 1.54 (s,3H-13).

13C-NMR (50.3 MHz) CDCl3/TMS (d = ppm): 166.60 (C=O); 149.06 (C-1); 146.19 (C-7); 146.10 (C-6); 144.17 (C-4); 137.31 (C-5); 132.36 (C-9); 133.38 (C-2); 125.82 (C-10); 112.87 (C-3); 108.04 (C-5); 105.29 (C-8); 100.68 (OCH2O); 75.79 (C-1); 59.57 (C-3); 48.54 (C-11); 29.03 (C-4); 27.15 (C-13).

(Z) Isomer

1H-NMR (200 MHz) CDCl3/TMS (d = ppm): 9.40 (s,1H,NH); 7.60 (s,1H,H-5); 6.64 (s,1H,H-8); 6.44 (s,1H,H-5); 5.88 (s,2H,OCH2O); 4.0 (m, 2H-3); 3.45 (d,J = 14, 1H,H-11); 3.03 (d,J = 14, 1H,H-11); 2.90 (m, 2H-4); 1.60 (s, 3H-13).

13C-NMR (50.3 MHz) CDCl3/TMS (d = ppm): 172.78 (C=O); 149.19 (C-1); 145.77 (C-7); 145.70 (C-6); 144.00 (C-4); 134.54 (C-9); 137.39 (C-5); 111.63 (C-5); 111.63 (C-8); 100.50 (OCH2O); 75.79 (C-1); 59.71 (C-3); 43.31 (C-11); 28.75 (C-4); 28.33 (C-13).

1-(1-Methyl-6,7-methilenedioxy)-isochromanyl-acetylarylhydrazone of 4-dimethylaminobenzaldeyde (3c-(E),(Z))

m.p.: 93-94 °C

I.R. (KBr) n: 3450, 3201 (NH); 1655 (C=O) cm-1.

M.S.(70 eV) m/z: 395 (4%); 191 (100%); 149 (50%); 148 (65%); 135 (18%); 77 (18%).

(E) Isomer

1H-NMR (200 MHz) CDCl3/TMS (d = ppm): 9.64 (s,1H,NH); 7.83 (s,1H,H-7); 7.57 (d,J = 9,2H,H-26); 6.62 (d,J = 9,2H,H-35); 6.59 (s,1H,H-8); 6.49 (s,1H,H-5); 5.9 (m,2H,OCH2O); 4.1 (m, 2H-3); 2.9 (m, 2H-4); 2.98 (s,N(CH3)2); 2.9 (d,J = 14, 2H-11); 2.8 (d,J = 14, 2H-11); 1.55 (s, 3H-13).

13C-NMR (50.3 MHz) CDCl3/TMS (d = ppm).: 165.84 (C=O); 151.44 (C-4); 147.90 (C-7); 146.19 (C-6); 146.17 (C-7); 132.52 (C-9); 128.89 (C-26), 125.76 (C-10); 120.96 (C-1); 111.32 (C-35); 108.14(C-5); 105.46 (C-8); 100.65 (OCH2O); 75.82 (C-1); 59.56 (C-3); 48.07 (C-11); 39.86 (N(CH3)2); 29.09 (C-4); 27.09 (C-13).

(Z) Isomer

1H-NMR (200 MHz) CDCl3/TMS (d = ppm):8.90 (s,NH); 7.58 (s,H-7); 7.47 (d,J = 9,H-26); 6.66 (d,J = 9,H-35); 6.61 (s,H-8); 6.52 (s,H-5); 5.9 m,OCH2O); 4.1 (m, 2H-3), 3.50 (d,J = 15, 2H-11); 3.06 (d,J = 15, 2H-11); 2.99 (s,N(CH3)2); 2.9 (m, 2H-4); 1.62 (s, 3H-13).

13C-NMR (50.3 MHz) CDCl3/TMS (d = ppm): 171.97 (C=O); 151.20 (C-4); 146.00(C-6,7); 144.48 (C-7); 134.76 (C-9): 128.16 (C-26); 126.33 (C-10); 121.54 (C-1); 111.55 (C35); 108.14 (C-5); 105.32 (C-8); 100.49 (OCH2O); 75.82 (C-1); 59.72 (C-3); 42.29 (C-11); 39.93 (N(CH3)2); 29.15 (C-4); 28.50 (C-13).

1-(1-Methyl-6,7-methylenedioxy)-isochromanyl-acetylarylhydrazone of m-nitrobenzaldehyde (3d-(E),(Z))

m.p.: 183-184 °C

I.R.. (KBr) n: 3393, 3193 (NH); 1665 (C=O) cm-1.

M.E.(70 eV): 397 (3%); 217 (6%) ; 191 (100%); 166 (17%); 135 (63%);77 (15%).

(E) Isomer

1H-NMR (200 MHz) CDCl3/TMS (d = ppm): 10.02 (s,NH); 8.43 (H-7); 8.20 (H-2) 8.11 (H-4); 7.90 (H-6); 6.58 (s,H-8); 6.49 (s,H-5); 5.87 (OCH2O); 3.98 (m, 2H-3); 2.89 (2H-11); 2.87 (2H-11); 2.84 (m, 2H-4); 1.55 (s, 3H-13).

13C-NMR(50.3 MHz) CDCl3/TMS (d = ppm): 166.91 (C=O); 148.35 (C-3); 146.67 (C-6,7); 144.88 (C-7); 135.67 (C-1); 132.58 (C-6); 132.33 (C-9); 129.56 (C-5); 124.38 (C-4); 122.25 (C-2); 108.43 (C-5); 105.47 (C-8); 100.96 (OCH2O); 76.10 (C-1); 59.97 (C-3); 48.96 (C-11); 29.37 (C-4); 27.36 (C-13).

(Z) Isomer

1H-NMR (200 MHz) CDCl3/TMS (d = ppm).: 9.96 (s,NH); 8.43 (H-7); 7.81 (H-6); 6.64 ( H-8); 6.57 ( H-5); 6.16 ( H-2); 5.82 ( OCH2O); 4.06 (m, 2H-3) 3.41(2H-11); 3.18 (2H-11); 2.84 (m, 2H-4).

13C-NMR (50.3 MHz) CDCl3/TMS (d = ppm).: 172.97 (C=O); 148.40 (C-3); 146.04 (C-6,7); 136.00 (C-7); 135.76 (C-1); 132.33 (C-9); 129.56 (C-5); 126.00 (C-10); 124.11 (C-4); 121.58 (C-2); 108.43 (C-5); 105.47 (C-8); 100.75 (OCH2O); 76.10 (C-1); 59.97 (C-3); 43.14 (C-11); 29.37 (C-4); 28.52 (C-13).

1-(1-Methyl-6,7-methylenedioxy)-isochromanyl acetylarylhydrazone of p-nitrobenzaldehyde (3e-(E),(Z))

m.p.: 226 228 °C

I.R. (KBr ) n: 3413, 3170 (NH); 1665 (C=O) cm-1.

M.E.: 397 (6%); 298 (22%); 191 (100%); 176 (32%); 149 (21%); 57 (22%).

(E) Isomer

1H-NMR (200 MHz) CDCl3/TMS (d = ppm).: 9.9 (s, NH); 8.70 (s, H-7); 8.23 (H-35); 7.86 (m, H-26); 6.52 (H-5); 6.50 (H-8); 5.89 (OCH2O); 4.05 (2H-3); 2.89 (2H-11); 2.67 (2H-4); 1.58 (3H-13).

13C-NMR(50.3 MHz) CDCl3/TMS (d = ppm).: 145.38 (C-6); 145.20 (C-7); 125.79 (C-10); 107.55 (C-5); 105.14 (C-8); 100.15 (OCH2O); 75.07 (C-1); 59.87 (C-3); 46.78 (C-11); 28.57 (C-4); 27.90 (C-13).

(Z) Isomer

1H-NMR (200 MHz) CDCl3/TMS (d = ppm).: 9.90 (NH); 8.33 (H-7); 8.19 (H-35); 7.85 (H-26); 6.52 (H-5); 6.60 (H-8); 5.89 (OCH2O); 4.05 (H-3); 2.89 (H-11); 2.67 (H-4); 1.51 (H-13).

13C-NMR (50.3 MHz) CDCl3/TMS (d = ppm).: 145.38 (C-6); 145.20 (C-7); 125.79 (C-10); 107.55 (C-5); 105.09 (C-8); 100.02 (OCH2O); 58.87 (C-3); 42.02 (C-11); 28.57 (C-4); 27.50 (C-13).

1-(1-Methyl-6,7-methylenedioxy)-isochromanyl-acetylarylhydrazone of p-methoxybenzaldehyde (3f-(E),(Z))

m.p.: 168-169 °C

I.R. (KBr) n: 3452, 3170 (NH); 1661 (C=O) cm-1.

(E) Isomer

1H-NMR (200 MHz) CDCl3/TMS (d = ppm).: 9.75 (s,NH); 7.92 (s,H-7); 7.85 (m,H-35); 7.56 (m,H-26); 6.58 (s,H-8); 6.48 (s,H-5); 5.87 (s,OCH2O); 4.02 (m,2H-3); 3.79 (s,OCH3); 2.9 (d,J = 15,2H-11); 2.8 (d,J = 15,2H-11); 2.7 (m,2H-3); 1.55 (3H-13).

13C-NMR (50.3 MHz) CDCl3/TMS (d = ppm).: 166.20 (C=O); 161.23 (C-4); 147.06 (C-7); 146.49 (C-6); 146.42 (C-7); 132.55 (C-9); 129.05 (C-26); 126.67 (C-1); 125.85 (C-10); 113.90 (C-35); 108.26 (C-5); 105.26 (C-8); 100.79 (OCH2O); 59.72 (C-3); 55.16 (OCH3); 48.43 (C-11); 29.22 (C-4); 27.20 (C-13).

(Z) Isomer

1H-NMR (200 MHz) CDCl3/TMS (d = ppm).: 9.34 (s,NH); 7.85 (m, H-35); 7.65 (s,H-7); 7.56 (m,H-26); 6.65 (s,H-8); 6.49 (s, H-5); 5.87 (s,OCH2O); 4.02 (m, 2H-3); 3.45 (d,J = 13, 2H-11); 3.07 (d,J = 13, 2H-11); 2.7 (m, 2H-3); 1.62 (s, 3H-13).

13C-NMR (50.3 MHz) CDCl3/TMS (d = ppm: 172.39 (C=O); 160.94 (C-4); 145.92 (C-6); 145.78 (C-7); 143.32 (C-7); 134.77 (C-9); 128.42 (C-26); 126.52 (C-1); 126.30 (C-10); 114.05 (C-35); 108.26 (C-5), 105.42 (C-8); 100.59 (OCH2O); 59.86 (C-3); 55.16 (OCH3); 42.60 (C-11); 29.22 (C-4); 28.40 (C-13).

1-(1-Methyl-6,7-methylenedioxy)-isochromanyl-acetylarylhydrazone of p-bromobenzaldehyde (3g-(E),(Z))

m.p.: 178-181 °C

máx. (KBr) n: 3450, 3180 (NH); 1662 (C=O) cm-1.

(E) Isomer

1H-NMR (200 MHz) CDCl3/TMS (d = ppm).: 9.85 (s,NH); 7.99 (s,H-7); 7.7-7.2 (H-26); 7.7-7.2 (H-35); 6.58 (s,H-8); 6.49 (s,H-5); 5.89 (s,OCH2O); 4.03 (2H-3); 2.85 (d,J = 15, 2H-11); 2.82 (d,J = 15, 2H-11); 2.67 (2H-4); 1.62 (s, 3H-13).

13C-NMR (50.3 MHz) CDCl3/TMS (d = ppm).: 166.53 (C=O); 146.46 (C-6); 146.35 (C-7); 145.88 (C-7); 132.85 (C-9); 132.22 (C-1); 131.66 (C-35); 128.82 (C-26); 125.78 (C-10); 124.38 (C-4); 108.30 (C-5); 105.38 (C-8); 100.87 (OCH2O); 59.78 (C-3); 48.51 (C-11); 29.22 (C-4); 27.21 (C-13).

(Z) Isomer

1H-NMR (200 MHz) CDCl3/TMS (d = ppm).: 9.67 (s,NH); 7.67 (s,H-7); 7.7-7.2 (H-26); 7.7-7.2 (H-35); 6.63 (H-8); 6.51 (s); 5.83 (OCH2O); 3.84 (m, 2H-3); 3.48 (d,J = 13, 2H-11); 3.11 (d,J = 13, 2H-11); 2.67 (m, 2H-4); 1.71 (s, 3H-13).

13C-NMR (50.3 MHz) CDCl3/TMS (d = ppm).: 172.89 (C=O); 146.46 (C-6); 146.35 (C-7); 142.43 (C-7); 134.50 (C-9); 132.52 (C-1); 131.80 (C-35); 128.30 (C-26); 126.52 (C-10); 123.93 (C-4); 108.30 (C-5); 105.50 (C-8); 100.68 (OCH2O); 75.90 (C-1); 59.91 (C-3); 42.61 (C-11); 29.22 (C-4); 28.41 (C-13).

Pharmacology

The analgesic activity was determined in vivo using the abdominal constriction test induced by 0.6% acetic acid (0.1 mL/10 g) in albino mice24 (ca. 20 g); indomethacin was used as the standard. The solution of acetic acid was administered i.p. and the number of constrictions was registered for 30 min (control). All compounds were administered p.o. in arabic gum (5%) in a dose of 100 mM/kg (0.1 mL/20g) 1 h before the injection of the acetic acid solution. The data were statistically analyzed by the Student t-test, with the significance level set at P < 0.05.

Results and Discussion

The synthesis of new compounds (3a-g) was carried out by exploring the previously described ester (5)16 synthesized from natural safrole (4) in 80% yield. This synthetic route uses as key step an acid-catalyzed intramolecular alkylation of the 6-position of the aromatic system of the hemiketal intermediate (7), formed in situ from the condensation of homopiperonilic alcohol (8) with ethylacetoacetate (9), in the presence of the catalytic amount of p-toluenesulfonic acid,as indicated in Scheme 2. The isochromanylacylhydrazide (6), precursor of the desired derivatives (3), was prepared in 85% yield by the conventional treatment of an ethanolic solution of 1-alkyl-1-isochroman ester (5) with 85% hydrazine hydrate, at reflux, to furnish (6) in 85% yield, as outlined in Scheme 3. Finally, the target compounds (3a-g) were prepared in high yield by acidic condensation of (6) with the appropriate aldehydes20 (Table 1). The pattern and choice of the substituent (Ar-W), present in the acylarylhydrazone derivatives (3a-g), was determined by the need to introduce a significant difference in the electronic character in this framework21, in order to study the eventual contribution of these structural modifications to bioactivity. Apart from this, the presence of an N-dimethylaminophenyl unit present in (3b) was indicated by the previously described potent analgesic activity detected in compound (2)11.

These new derivatives (3a-g) were fully characterized spectroscopically. For instance, in the infrared spectra the presence of a strong absorption at n 3450 cm-1 is attributed to an -NH group, indicating that the acylhydrazone form predominates over the azo form (Fig. 1)22. Careful analysis of hydrogen and carbon-13 nuclear magnetic resonance (NMR) spectra of these derivatives (3a-g) indicated the presence of a diastereomeric mixture at the C=N double bond level, in a 70:30 ratio favoring the (E)-isomer. The analysis of the homonuclear (1Hx1H-COSY) and heteronuclear 1Hx13C-COSY:modulated with 1JCH and nJCH (n = 2 and 3,COLOC) 2D shift-correlated spectra confirmed this assumption, especially by the pattern presented by the H-7, C-7, CH2-11, C-12 and NH-12, indicating that the (Z)-isomer resonates at a higher magnetic field than the (E)-isomer (Table 2).


These new isochromanylarylacetylhydrazone derivatives (3a-g) were evaluated for their analgesic and anti-inflammatory activities. Unfortunately, these compounds were not effective as anti-inflammatory agents, as observed in the carrageenan-induced rat paw edema test23. In this bioassay, only compound 3 g, where W=Br, presented significant activity, inhibiting paw edema in 30.9% in a dose of 100 mmol/kg p.o. The anti-inflammatory test results indicated that the enhanced lipophilicity of the p-bromophenyl template may contribute to the observed activity. The analgesic activity of these compounds was investigated (Table 3) by the inductive abdominal constrictions test in mice24, using indomethacin at 30 mmol/kg, p.o., as a standard. The compound possessing the 4-dimethylaminophenyl moiety at the acylhydrazone framework (3c), was the most potent one. In fact, this result seems to indicate, as observed in an other series previously synthesized in our laboratory25, that the presence of this functionality could have an important role in analgesic activity (Fig. 2), probably acting as a hydrogen bond donor in the interaction with the bioreceptor.


Conclusions

The synthetic methodology used in this work was shown to be efficient for obtaining of new isochromanylacetylhydrazone compounds (3a-g) in high yields, using natural safrole as the starting material. These compounds represent a new class of non-addictive analgesic agents.

The hydrogen and carbon-13 nuclear magnetic resonance (NMR) spectra and assignments by the homonuclear (1Hx1H-COSY) and heteronuclear 1Hx13C-COSY:modulated with 1JCH and nJCH (n = 2 and 3, COLOC) 2D shift-correlated spectra showed that the (E) diastereoisomer makes a major contribution in the desired compound (3).

The results described reinforce, as previously observed in an other related series of acylhydrazones synthesized in our laboratory25, that the acylhydrazone moiety is an important pharmacophore group for the observed activity, and that the N-dimethyl substituent at position 4 of the phenyl ring is essential for analgesic activity. The mechanism of the action of these new compounds is currently under investigation in our laboratory and will be disclosed in the future.

Acknowledgments

We are grateful to CNPq (#52.0511/94-3), FAPERJ (E-120-33/5), and FUJB-UFRJ (BR) for the financial support for this work, and to CNPq and CAPES (BR) for fellowships ( MRLS, ALPM, and EJB). The authors thank Prof. Mario Geraldo (UFRRJ-BR) for the NMR spectra, the referees for the valuable suggestions, and S. de C. Parrini, K.C.M. da Silva, G. Barreiro, and Dr. A.L.P. de Miranda (LASSBio, UFRJ-BR) for the biological data.

  • 1. Handwerker, H.O. Sensory Functions of Skin; Pergamon Press, Oxford ,1976; p. 427.
  • 2. Ferreira, S.H.; Moncada, S.; Vane, J.R. Br. J. Pharmacol. 1973, 49, 86.
  • 3. Schepelmann, K.; Mebllinger, K.; Schaible, H-G.; Schimdt, R.F. Neuroscience 1992, 50, 237.
  • 4. Meade, E.A.; Smith, W.L.; De Witt, D.L. J. Biol. Chem. 1993, 268, 6610.
  • 5. Kujubu, D.A.; Fletcher, B.B.S.; Varnum, B.C.; Lim, R.W.; Herschman, H.R. J. Biol. Chem. 1991, 266,12866.
  • 6. Patrignani, P.; Panara, M.R.; Greco, A.; Fusio, O.; Natoli, C.; Iacobelli, S.; Cipollone, F.; Ganci, A.; Créminon, C.; Maclouf, J.; Patrono, C. J. Pharmacol. Exp. Ther. 1994, 271, 1705.
  • 7. Flower, R.J.; Vane, J.R. Biochem. Pharmacol. 1974, 23, 1439.
  • 8. Bray, M. A. Agents Action 1986, 19, 87.
  • 9. Brain, S.D.; Williams, T.J. Pharmac. Ther 1990, 46, 57.
  • 10. Barreiro, E.J.; Costa, P.R.R.; Barros, P.R.V.R.; de Mello, R.T. An. Acad. Bras. Cienc 1981, 53, 65.
  • 11. Matheus, M.E.; Oliveira, L.F.; Freitas, A.C.C.; Carvalho, A.M.A.S.P.; Barreiro, E.J. Braz. J. Med. Biol. Res. 1991, 24, 1219.
  • 12. Silveira, I.A.B.F.; Paulo, L.G.; Miranda, A.L.P.; Rocha, S.O.; Freitas, A. C. C.; Barreiro, E.J. J. Pharm. Pharmacol. 1993, 45, 646.
  • 13. Fraga, C.A.M.; Barreiro, E.J. J. Heterocyclic Chem. 1992, 29, 1667.
  • 14. Freitas, A.C.C.; Barreiro, E.J. J. Heterocyclic Chem 1992, 29,407.
  • 15. Lima, M.E.F.; Barreiro, E.J. J. Pharm. Sciences 1992, 81, 1219.
  • 16. Silva, E.F.; Barreiro, E.J. J. Braz. Chem. Soc. 1993, 4, 40.
  • 17. Dias, L.R.S.; Alvim, M.J.F.; Freitas, A.C.C.; Barreiro, E.J., Miranda, A.L.P. Pharmac. Acta Helvetiae 1994, 69, 163.
  • 18. Freitas, A.C.C. PhD Thesis, Instituto de Química/ LASSBio, Universidade Federal do Rio de Janeiro, 1991.
  • 19. Barreiro, E.J.; Costa, P.R.R.; Coelho, F.A.S.; Farias, F.M.C. J. Chem. Res. (M) 1985, 2301.
  • 20. Santos, M.R.L.; Barreiro, E.J.; Braz-Filho, R. Abstracts of18a Reunião Anual da Sociedade Brasileira de Química, Braz. Chem. Soc., Caxambu, Brazil, 1995, Abstr. QO-074.
  • 21. Kubiniy, H. Hansch Analysis and Related Approaches; Weinheim, Germany, 1993, p 23.
  • 22. Szileigye, G.; Kaszheimer, E.; Matyus, P.; Kosary, J.; Czarc, K.; Czen, G.; Huszti, Z.; Tardos, L.; Kcsa, E.; Jaszlits, L. Eur. J. Med. Chem. 1984, 19, 111.
  • 23. Ferreira, S.H. J. Pharm. Pharmacol. 1979, 31, 648.
  • 24. Whittle, B.A. Br. J. Pharmacol. 1964, 22, 246.
  • 25. Miranda, A.L.P.; Santos, M.R.L.; Lima, P.; Barreiro, E.J.; Braz-Filho, R.; Silva, K.C.M.; Parrini, S.C.; Abstracts of X Reunião Anual da Federação de Sociedade de Biologia Experimental , Caxambu, Brazil, 1995, Abstr. 19.006.

Publication Dates

  • Publication in this collection
    10 Sept 2010
  • Date of issue
    1997

History

  • Accepted
    02 Dec 1996
  • Received
    29 Mar 1996
Sociedade Brasileira de Química Instituto de Química - UNICAMP, Caixa Postal 6154, 13083-970 Campinas SP - Brazil, Tel./FAX.: +55 19 3521-3151 - São Paulo - SP - Brazil
E-mail: office@jbcs.sbq.org.br